Carrier billing lets you buy apps, games, or services and charge the cost...

https://harpersnewinsight.brightsora.com/posts/why-does-carrier-billing-show-up-as-a-weird-line-item-on-your-bill

Carrier billing lets you buy apps, games, or services and charge the cost directly to your phone bill. This means the payment shows up on your monthly statement or is taken from your prepaid credit if you use pay-as-you-go